An extensive summary of nanoparticles is provided as key enablers in modern optoelectronic devices, highlighting their fundamental principles, synthesis methods, technological evolution, and societal impact. Nanomaterials exhibit distinct physical and electronic properties arising from quantum confinement, large surface area, and tunable bandgaps. Their classification based on dimensionality, composition and functionality demonstrates their versatility across diverse optoelectronic applications such as photovoltaics, LEDs, photodetectors, lasers, and modulators. The chapter presents the chronological development from early semiconductor devices to advanced hybrid and 2D materials, including perovskites, quantum dots and transition metal dichalcogenides, which have redefined performance metrics in terms of efficiency, flexibility, and scalability. Detailed discussions on synthesis approaches i.e. top-down (milling, lithography, sputtering) and bottom-up (CVD, sol–gel, hydrothermal, colloidal methods) illustrate the pathways for fabricating nanostructures with controlled morphology and crystallinity. Applications in energy harvesting, display technologies, quantum communication and neuromorphic systems demonstrate their transformative role in sustainable and intelligent technologies. Despite remarkable progress, challenges such as instability, environmental risks, and manufacturing scalability persist. Future perspectives emphasize machine learning-assisted material design, green synthesis, and circular economy approaches to ensure safe and sustainable integration. Overall, the chapter underscores nanomaterials as the cornerstone of next-generation optoelectronic innovation, bridging physics, chemistry and engineering toward energy-efficient, flexible and multifunctional devices.